JP5035913B2 - Etching solution preparation method, etching method and etching apparatus - Google Patents

Description

  The present invention relates to a method for preparing an etching solution in which a desired amount of liquid tetraethoxysilane (hereinafter referred to as “TEOS”) is dissolved to prepare a phosphoric acid solution, and a desired amount in a phosphoric acid solution being circulated at high temperature. The present invention relates to an etching method and an etching apparatus for etching a silicon nitride film formed on a semiconductor silicon substrate using a phosphoric acid solution by dissolving the TEOS.

  The high-temperature phosphoric acid solution at 120 to 180 ° C. used for semiconductor substrate processing is not only silicon nitride but also silicon oxide, which is about 1/30 of silicon nitride, but has etching characteristics.

  In most cases of etching a silicon nitride film with high-temperature phosphoric acid, a silicon oxide film is also present on the surface of the substrate. Therefore, in order to suppress the etching of the silicon oxide film, the treatment is performed with silicon dissolved in a phosphoric acid solution. The technique to do is taken.

  As an example, when a silicon compound is added so that the silicon concentration in the phosphoric acid solution is 50 ppm or more in the 155 ° C. phosphoric acid treatment, the nitrogen compound film can be etched without etching the silicon oxide film at all. .

  As a conventional method for dissolving a silicon compound in a phosphoric acid solution, a product lot in which etching of a silicon oxide film is allowed to some extent or a dummy lot having a silicon nitride film on a silicon substrate is used to obtain a desired silicon concentration. A method has been adopted in which a product that does not permit etching of a silicon oxide film is processed.

  In addition, as disclosed in Patent Document 1, there is a proposal that TEOS is dissolved in a solvent such as ethanol and then added to a phosphoric acid solution to dissolve silicon.

  However, when a product lot is used for dissolving silicon, the amount of silicon dissolved is limited by the convenience of the product lot, so that a desired amount of silicon cannot be dissolved in the phosphoric acid solution at a desired timing.

  In addition, a dummy lot with a silicon nitride film on a silicon substrate is used to dissolve silicon. However, since a high cost and labor are required to prepare the dummy lot, it should be done regularly. Is not realistic.

  Further, the technique of Patent Document 1 is basically a technique in which silicon is dissolved in an unused phosphoric acid solution. Since TEOS is dissolved in a solvent such as ethanol, high-temperature phosphoric acid flowing at 120 to 180 ° C. When used in a solution, a solvent such as ethanol evaporates to form a silicic acid condensate, which has a disadvantage that cannot be applied.

  Further, if liquid TEOS is simply added to the phosphoric acid solution, the silicon component of TEOS forms a silicic acid condensate having a large molecular weight. This silicic acid condensate is a cloudy solid, which is dissolved by phosphoric acid. However, if its molecular weight is large, it will take a long time to dissolve, and it will clog the circulating filter in the phosphoric acid solution and hinder circulation operation of the phosphoric acid solution. give.

JP 2000-58500 A

  The problem to be solved by the present invention is to solve the above-mentioned conventional problems, and to easily and quickly add a desired amount of a silicon compound into a flowing phosphoric acid solution by the above-described technique for dissolving silicon in a phosphoric acid solution. An etching solution preparation method, an etching method, and an etching apparatus are provided.

In order to solve the above-mentioned problems, the present invention mixes liquid TEOS with water or gas, and then adds this to a phosphoric acid solution flowing at 120 ° C. to 180 ° C. at a rate of 1 to 5 ml / min to dissolve TEOS. And preparing an etching solution preparation method characterized by preparing a phosphoric acid solution having a silicon concentration of 30 to 80 ppm .

According to a second means of solving the present invention, in the etching solution preparation method, the gas mixed in the liquid TEOS is at least one selected from the group consisting of water vapor, air, nitrogen gas, or rare gas. There is to be.

  The third solving means of the present invention is that the gas mixed with the liquid TEOS is nitrogen gas in the method for preparing an etching solution.

According to a fourth solution of the present invention, in an etching method for etching a silicon nitride film formed on a semiconductor substrate using a phosphoric acid solution in an etching tank, liquid TEOS is mixed with water or gas, this was added in 1-5 ml / min into the circulation line of the phosphoric acid solution flowing in the circulation operation at 120 ° C. to 180 ° C., the silicon concentration by dissolving the T EOS prepare a phosphoric acid solution of 30～80Ppm, this An etching method for etching a silicon nitride film formed on a semiconductor substrate using a phosphoric acid solution is provided.

According to a fifth solution of the present invention, in the above etching method, the gas mixed in the liquid TEOS is at least one selected from the group consisting of water vapor, air, nitrogen gas, or a rare gas. is there.

A sixth solution of the present invention is that, in the above etching method, the gas mixed with the liquid TEOS is nitrogen gas.

The seventh solving means of the present invention includes an etching tank for etching a silicon nitride film formed on a semiconductor substrate using a flowing phosphoric acid solution, and a circulation line for circulating the phosphoric acid solution at 120 ° C. to 180 ° C. And a line for supplying liquid TEOS, a line for supplying water or gas, and a line for mixing liquid TEOS and water or gas and supplying this to the circulation line at a rate of 1 to 5 ml / min. Then, a desired amount of TEOS is dissolved to prepare a flowing phosphoric acid solution having a silicon concentration of 30 to 80 ppm , and this flowing phosphoric acid solution is circulated and used to form silicon nitride formed on the semiconductor substrate in the etching tank. An etching apparatus for etching a film is configured.

  According to the present invention, an etching solution can be prepared by dissolving a desired amount of a silicon compound in a phosphoric acid solution easily and quickly as compared with the prior art, and a semiconductor substrate using a high-temperature phosphoric acid solution. In the upper silicon nitride film etching method, the silicon compound film can be stably etched using a phosphoric acid solution circulating at a high temperature, and the process performance can be improved and the amount of phosphoric acid waste liquid can be reduced. A device can be provided.

  Hereinafter, an etching solution preparation method, an etching method, and an etching apparatus according to the present invention will be described in detail with reference to the drawings.

First, the preparation method of the etching solution according to the present invention will be described in detail.
Liquid TEOS is mixed with deionized water (hereinafter, all referred to as “DIW”), and then added to a flowing phosphoric acid solution little by little to dissolve a desired amount of TEOS to prepare a phosphoric acid solution. The flowing phosphoric acid solution includes using a flowing phosphoric acid solution or using the phosphoric acid solution while flowing.

  Further, in the present invention, liquid TEOS may be mixed with a certain kind of gas instead of mixing with DIW. The gas to be mixed is most preferably nitrogen gas because of its ease of operability, but water vapor, air, or a rare gas can be used in addition to nitrogen gas. The noble gas is a general term for helium, neon, argon, krypton, xenon, and radon in Group 18 of the periodic table.

Moreover, in this invention, it is preferable to adjust so that the silicon concentration of TEOS melt | dissolved in the phosphoric acid solution may be 30-80 ppm.
If the silicon concentration is 30 ppm or less, the desired silicon concentration is not achieved and the effect of addition is insufficient. On the other hand, if it is 80 ppm or more, silicon is deposited on the silicon substrate, which is not preferable.

  The reaction formula in the present invention is shown below. However, the chemical formula shown here is only an assumption and does not limit the present invention.

  Formula (1-1) is a chemical formula for hydrolysis that occurs when TEOS is added to the phosphoric acid solution. When TEOS is added to the phosphoric acid solution, protons in the phosphoric acid solution act on the bond of the ethyl group of TEOS, so that hydrolysis occurs immediately. TEOS becomes silicic acid and ethanol after hydrolysis, and ethanol is discharged as gas from the phosphoric acid solution.

  Formula (1-2) is a reaction formula in which silicic acid produced by hydrolysis of formula (1-1) is dissolved in phosphoric acid.

  Since the hydrolysis of TEOS occurs when H2O is present as shown in the formula (1-1), this reaction occurs even when TEOS is added to DIW, but the reaction rate is extremely slow. This reaction does not occur in the processing steps from mixing the TEOS in the invention to DIW to adding it to the phosphoric acid solution.

  Ideally, it is preferable that the reactions shown in the formulas (1-1) and (1-2) are performed. However, since silicic acid is a substance that easily condenses, the formula (2-1) As shown, a condensation reaction of silicic acid occurs simultaneously with the hydrolysis of TEOS, and a silicic acid condensate is generated.

  The silicic acid condensate generated in the formula (2-1) dissolves in phosphoric acid as shown in the formula (2-2). However, as described above, when the molecular weight of the silicic acid condensate increases, it takes time to dissolve in phosphoric acid. In addition, the silicic acid condensate may be clogged in the circulation filter and the like, which may hinder the circulation operation of the phosphoric acid solution.

  However, when TEOS is mixed with water or gas as proposed in the present invention and then added gradually to the phosphoric acid solution, TEOS is added while diffusing, and the above problem is solved.

  That is, in the present invention, in order to prevent TEOS from being diffused into the phosphoric acid solution at the same time as the TEOS is added to the phosphoric acid solution and forming a silicic acid condensate having a large molecular weight, In an apparatus or the like, TEOS is added to a flowing 25 to 180 ° C. phosphoric acid solution with stirring at a rate of 1 to 5 ml / min in 10 to 100 times its volume of DIW. In order to uniformly diffuse TEOS without condensing, about 10 times DIW is required. On the other hand, when DIW is 1000 times or more, it takes too much time to volatilize DIW thereafter.

  Thereafter, the phosphoric acid solution is heated at 140 to 180 ° C. for 30 to 60 minutes to volatilize the ethanol generated by the hydrolysis of TEOS and the excessively added DIW.

  Next, the etching method and the etching apparatus according to the present invention will be described in detail.

  FIG. 1 is a view showing an embodiment of an etching apparatus according to the present invention, wherein 1 is an etching tank for performing high-temperature phosphoric acid treatment, and 2 is a phosphoric acid solution for sending a phosphoric acid solution from the etching tank 1 to a high-temperature chemical solution circulation device 4. A circulation line 3 is a phosphoric acid solution circulation line for sending a phosphoric acid solution from the high-temperature chemical circulation device 4 to the bottom of the etching tank 1. 5 is a circulation pump for circulating the phosphoric acid solution, 6 is a circulation filter, 7 is a line heater for heating the phosphoric acid solution, and 8a is for replenishing water lost by volatilization from the high-temperature chemical solution. The DIW supply line 8 b is a mixing line that mixes DIW supplied from the DIW addition line 8 a and TEOS supplied from the TEOS supply line 13 and supplies the mixed liquid to the phosphoric acid solution circulation line 3. The high-temperature chemical solution circulation device 4 is the same as the device used in the high-temperature etching solution circulation method described in Japanese Patent Laid-Open No. 2-96334, and the present invention provides preferable results when used in combination with this circulation device. It is done.

  Reference numeral 9 denotes a TEOS supply tank. The TEOS is added from the TEOS supply line 10 through the syringe pump 11 and the TEOS supply line 13 to the DIW supply line 8a, and then supplied to the phosphoric acid solution circulation line 3 through the mixing line 8b. The 12 is a TEOS return line from the syringe pump to the TEOS supply tank, 14 is a nitrogen gas supply line for purging the TEOS supply line 13, and 15 is a drain line.

  Hereinafter, an example of the etching method of the present invention will be described. First, the necessary TEOS addition amount is calculated from the amount of silicon desired to be dissolved in the phosphoric acid solution and the phosphoric acid solution high-temperature circulation system 4 that are operating at high temperature circulation at 120 to 180 ° C.

Next, TEOS is quantified using the syringe pump 11 and added to the circulating phosphoric acid solution pipe together with DIW at 1 to 5 ml / min. TEOS is stored in the TEOS supply tank 9, and the TEOS in the TEOS supply tank 9 is added from the TEOS supply line 10 to the DIW supply line 8a via the syringe pump 11 and the TEOS supply line 13, and then mixed in the mixing line 8b. Then, it is supplied to the phosphoric acid solution circulation line 3. Excess TEOS is returned from the syringe pump 11 to the TEOS supply tank 9 via the TEOS return line 12.
After the addition of TEOS, the TEOS in the TEOS supply line 10 is purged with nitrogen gas supplied from the nitrogen gas supply line 14 and discharged from the waste liquid line 15 together with DIW.

  Next, circulation operation is performed at 140 to 180 ° C. for 30 to 60 minutes in the phosphoric acid solution high-temperature circulation system 4 to vaporize ethanol generated by hydrolysis of TEOS and excessively added water.

  When the silicon concentration in the phosphoric acid solution before addition of TEOS cannot be predicted, the silicon concentration can be easily measured by using it together with the silicon concentration measuring device in the phosphoric acid solution described in JP-A-2006-352097.

  In conjunction with this, if used together with the phosphoric acid solution regenerating apparatus described in JP-A No. 2004-134780, the phosphoric acid solution being used at high temperature is changed to a desired concentration at a desired timing to perform etching treatment. It is also possible to do this.

  Next, an Example is given and this invention is demonstrated further in detail. However, the examples are merely examples, and the present invention is not limited to these examples.

  The etching apparatus shown in FIG. 1 was used.

<Example 1>
After adding TEOS, 40 ml at 55 ml / min, mixed with DIW 10 times its volume at 25 ml / min in 55 ml of 86% by weight phosphoric acid solution circulating at 155 ° C. Heating circulation operation was performed at 155 ° C. for 1 hour. Moreover, ICP-AES analysis of the silicon concentration in the phosphoric acid solution and the etching rate measurement of the silicon nitride film and the silicon oxide film on the silicon substrate were performed before and after the addition of TEOS.

  Table 1 shows the results of measuring the silicon concentration in the phosphoric acid solution before and after the addition of TEOS by ICP-AES analysis and the silicon penetration amount calculated therefrom. The amount of silicon in the added TEOS and 40 milliliters is 5.02 grams, which is almost the same as the amount actually dissolved in the phosphoric acid solution. Therefore, it can be said that almost all silicon in the added TEOS is dissolved in the phosphoric acid solution.

  From this, it can be said that the amount of silicon dissolved in the phosphoric acid solution can be adjusted by adjusting the TEOS addition amount.

  Table 2 shows the etching rate measurement results of the silicon oxide film and the silicon nitride film before and after the addition of TEOS. The etching rate of the silicon oxide film after addition of TEOS is negative because the etching concentration of the silicon oxide film is suppressed due to the increase in the concentration of silicon in the phosphoric acid solution, and the adsorption reaction of the silicon compound is dominant. This is because the silicon compound is adsorbed on the surface of the silicon oxide film. The silicon oxide film that had been etched at 0.09 nanometer / minute before the addition of TEOS had an etching rate of -0.01 nanometer / minute after the addition of TEOS, and the silicon oxide film was not etched at all. It was confirmed that the film could be etched.

<Example 2>
Next, using the etching apparatus of FIG. 1, TEOS, 60 ml in 55 liters of 86 mass% phosphoric acid solution circulating at 155 ° C. was replaced with DIW for mixing at 2.5 ml / min, After mixing with nitrogen gas at 30 ml / min and adding, heating circulation operation was performed at 155 ° C. for 1 hour. Similarly to Example 1, before and after addition of TEOS, ICP-AES analysis of the silicon concentration in the phosphoric acid solution and measurement of the etching rate of the silicon nitride film and the silicon oxide film on the silicon substrate were performed.

  Table 3 shows the results of measuring the silicon concentration in the phosphoric acid solution before and after the addition of TEOS by ICP-AES analysis and the silicon penetration amount calculated therefrom. The amount of silicon in the added TEOS and 60 ml is calculated to be 7.52 grams, which is almost the same as the amount actually dissolved in the phosphoric acid solution. Therefore, even when TEOS is added using nitrogen, it can be said that almost all silicon in TEOS is dissolved in the phosphoric acid solution.

  Table 4 shows the etching rate measurement results of the silicon oxide film and the silicon nitride film before and after the addition of TEOS. Before the addition of TEOS, the silicon oxide film etched at 0.11 nanometer / minute is etched after the addition of TEOS. It was confirmed that the silicon nitride film could be etched without etching the silicon oxide film at all even when the rate was -0.02 nanometer / min and TEOS was added while mixing with nitrogen.

  As a result, it has been found that according to the present invention, a desired amount of silicon can be accurately dissolved in the phosphoric acid solution.

  According to the present invention, it is possible to easily and quickly dissolve a desired amount of silicon in a phosphoric acid solution as compared with the prior art, and a process for etching a silicon nitride film on a semiconductor substrate using a high-temperature phosphoric acid solution In addition, by mounting on a silicon compound film etching apparatus using high-temperature phosphoric acid, the process performance can be improved and the amount of phosphoric acid waste liquid can be reduced.

It is drawing which shows the one aspect | mode of the etching apparatus by this invention.

Explanation of symbols

1: Etching tank 2: Phosphoric acid solution circulation line 3: Phosphoric acid solution circulation line 4: High-temperature chemical solution circulation device 5: Circulation pump 6: Circulation filter 7: Line heater 8a: DIW supply line 8b: Mixing line 9: TEOS supply tank 10: TEOS supply line 11: syringe pump 12: TEOS return line 13: TEOS supply line 14: nitrogen gas supply line 15: drainage line

Claims (7)

  After liquid tetraethoxysilane is mixed with water or gas, it is added to a phosphoric acid solution flowing at 120 ° C. to 180 ° C. at a rate of 1 to 5 ml / min to dissolve tetraethoxysilane and a silicon concentration of 30 to 30 ° C. A method for preparing an etching solution, comprising preparing an 80 ppm phosphoric acid solution.   The method for preparing an etching solution according to claim 1, wherein the gas mixed with the liquid tetraethoxysilane is at least one selected from the group consisting of water vapor, air, nitrogen gas, or a rare gas.   The method for preparing an etching solution according to claim 2, wherein the gas mixed with liquid tetraethoxysilane is nitrogen gas.   In an etching method for etching a silicon nitride film formed on a semiconductor substrate using a phosphoric acid solution in an etching tank, liquid tetraethoxysilane is mixed with water or gas, and then this is circulated at 120 ° C. to 180 ° C. 1 to 5 ml / min is added to the circulating line of the flowing phosphoric acid solution, tetraethoxysilane is dissolved to prepare a phosphoric acid solution having a silicon concentration of 30 to 80 ppm, and this phosphoric acid solution is used on the semiconductor substrate. An etching method comprising etching a silicon nitride film to be formed.   5. The etching method according to claim 4, wherein the gas mixed with the liquid tetraethoxysilane is at least one selected from the group consisting of water vapor, air, nitrogen gas, or a rare gas.   The etching method according to claim 4, wherein the gas mixed with the liquid tetraethoxysilane is nitrogen gas. An etching tank for etching a silicon nitride film formed on a semiconductor substrate using a flowing phosphoric acid solution, a circulation line for circulating the phosphoric acid solution at 120 ° C. to 180 ° C. , and a line for supplying liquid tetraethoxysilane A line for supplying water or gas, a line for mixing liquid tetraethoxysilane and water or gas, and supplying this to the circulation line at a rate of 1 to 5 ml / min. Dissolving and preparing a flowing phosphoric acid solution having a silicon concentration of 30 to 80 ppm, and circulating and using the flowing phosphoric acid solution to etch the silicon nitride film formed on the semiconductor substrate in the etching tank. Etching device characterized.